--- embedaddon/pcre/doc/pcreunicode.3 2012/02/21 23:05:52 1.1.1.1 +++ embedaddon/pcre/doc/pcreunicode.3 2012/02/21 23:50:25 1.1.1.2 @@ -1,26 +1,56 @@ .TH PCREUNICODE 3 .SH NAME PCRE - Perl-compatible regular expressions -.SH "UTF-8 AND UNICODE PROPERTY SUPPORT" +.SH "UTF-8, UTF-16, AND UNICODE PROPERTY SUPPORT" .rs .sp -In order process UTF-8 strings, you must build PCRE to include UTF-8 support in -the code, and, in addition, you must call +From Release 8.30, in addition to its previous UTF-8 support, PCRE also +supports UTF-16 by means of a separate 16-bit library. This can be built as +well as, or instead of, the 8-bit library. +. +. +.SH "UTF-8 SUPPORT" +.rs +.sp +In order process UTF-8 strings, you must build PCRE's 8-bit library with UTF +support, and, in addition, you must call .\" HREF \fBpcre_compile()\fP .\" with the PCRE_UTF8 option flag, or the pattern must start with the sequence (*UTF8). When either of these is the case, both the pattern and any subject strings that are matched against it are treated as UTF-8 strings instead of -strings of 1-byte characters. PCRE does not support any other formats (in -particular, it does not support UTF-16). -.P -If you compile PCRE with UTF-8 support, but do not use it at run time, the +strings of 1-byte characters. +. +. +.SH "UTF-16 SUPPORT" +.rs +.sp +In order process UTF-16 strings, you must build PCRE's 16-bit library with UTF +support, and, in addition, you must call +.\" HTML +.\" +\fBpcre16_compile()\fP +.\" +with the PCRE_UTF16 option flag, or the pattern must start with the sequence +(*UTF16). When either of these is the case, both the pattern and any subject +strings that are matched against it are treated as UTF-16 strings instead of +strings of 16-bit characters. +. +. +.SH "UTF SUPPORT OVERHEAD" +.rs +.sp +If you compile PCRE with UTF support, but do not use it at run time, the library will be a bit bigger, but the additional run time overhead is limited -to testing the PCRE_UTF8 flag occasionally, so should not be very big. -.P -If PCRE is built with Unicode character property support (which implies UTF-8 -support), the escape sequences \ep{..}, \eP{..}, and \eX are supported. +to testing the PCRE_UTF8/16 flag occasionally, so should not be very big. +. +. +.SH "UNICODE PROPERTY SUPPORT" +.rs +.sp +If PCRE is built with Unicode character property support (which implies UTF +support), the escape sequences \ep{..}, \eP{..}, and \eX can be used. The available properties that can be tested are limited to the general category properties such as Lu for an upper case letter or Nd for a decimal number, the Unicode script names such as Arabic or Han, and the derived @@ -38,22 +68,19 @@ compatibility with Perl 5.6. PCRE does not support thi .SS "Validity of UTF-8 strings" .rs .sp -When you set the PCRE_UTF8 flag, the strings passed as patterns and subjects -are (by default) checked for validity on entry to the relevant functions. From -release 7.3 of PCRE, the check is according the rules of RFC 3629, which are -themselves derived from the Unicode specification. Earlier releases of PCRE -followed the rules of RFC 2279, which allows the full range of 31-bit values (0 -to 0x7FFFFFFF). The current check allows only values in the range U+0 to -U+10FFFF, excluding U+D800 to U+DFFF. +When you set the PCRE_UTF8 flag, the byte strings passed as patterns and +subjects are (by default) checked for validity on entry to the relevant +functions. From release 7.3 of PCRE, the check is according the rules of RFC +3629, which are themselves derived from the Unicode specification. Earlier +releases of PCRE followed the rules of RFC 2279, which allows the full range of +31-bit values (0 to 0x7FFFFFFF). The current check allows only values in the +range U+0 to U+10FFFF, excluding U+D800 to U+DFFF. .P -The excluded code points are the "Low Surrogate Area" of Unicode, of which the -Unicode Standard says this: "The Low Surrogate Area does not contain any -character assignments, consequently no character code charts or namelists are -provided for this area. Surrogates are reserved for use with UTF-16 and then -must be used in pairs." The code points that are encoded by UTF-16 pairs are -available as independent code points in the UTF-8 encoding. (In other words, -the whole surrogate thing is a fudge for UTF-16 which unfortunately messes up -UTF-8.) +The excluded code points are the "Surrogate Area" of Unicode. They are reserved +for use by UTF-16, where they are used in pairs to encode codepoints with +values greater than 0xFFFF. The code points that are encoded by UTF-16 pairs +are available independently in the UTF-8 encoding. (In other words, the whole +surrogate thing is a fudge for UTF-16 which unfortunately messes up UTF-8.) .P If an invalid UTF-8 string is passed to PCRE, an error return is given. At compile time, the only additional information is the offset to the first byte @@ -85,43 +112,70 @@ situation, you will have to apply your own validity ch JIT optimization. . . -.SS "General comments about UTF-8 mode" +.\" HTML +.SS "Validity of UTF-16 strings" .rs .sp -1. An unbraced hexadecimal escape sequence (such as \exb3) matches a two-byte -UTF-8 character if the value is greater than 127. +When you set the PCRE_UTF16 flag, the strings of 16-bit data units that are +passed as patterns and subjects are (by default) checked for validity on entry +to the relevant functions. Values other than those in the surrogate range +U+D800 to U+DFFF are independent code points. Values in the surrogate range +must be used in pairs in the correct manner. .P -2. Octal numbers up to \e777 are recognized, and match two-byte UTF-8 -characters for values greater than \e177. +If an invalid UTF-16 string is passed to PCRE, an error return is given. At +compile time, the only additional information is the offset to the first data +unit of the failing character. The runtime functions \fBpcre16_exec()\fP and +\fBpcre16_dfa_exec()\fP also pass back this information, as well as a more +detailed reason code if the caller has provided memory in which to do this. .P -3. Repeat quantifiers apply to complete UTF-8 characters, not to individual -bytes, for example: \ex{100}{3}. +In some situations, you may already know that your strings are valid, and +therefore want to skip these checks in order to improve performance. If you set +the PCRE_NO_UTF16_CHECK flag at compile time or at run time, PCRE assumes that +the pattern or subject it is given (respectively) contains only valid UTF-16 +sequences. In this case, it does not diagnose an invalid UTF-16 string. +. +. +.SS "General comments about UTF modes" +.rs +.sp +1. Codepoints less than 256 can be specified by either braced or unbraced +hexadecimal escape sequences (for example, \ex{b3} or \exb3). Larger values +have to use braced sequences. .P -4. The dot metacharacter matches one UTF-8 character instead of a single byte. +2. Octal numbers up to \e777 are recognized, and in UTF-8 mode, they match +two-byte characters for values greater than \e177. .P -5. The escape sequence \eC can be used to match a single byte in UTF-8 mode, -but its use can lead to some strange effects because it breaks up multibyte -characters (see the description of \eC in the +3. Repeat quantifiers apply to complete UTF characters, not to individual +data units, for example: \ex{100}{3}. +.P +4. The dot metacharacter matches one UTF character instead of a single data +unit. +.P +5. The escape sequence \eC can be used to match a single byte in UTF-8 mode, or +a single 16-bit data unit in UTF-16 mode, but its use can lead to some strange +effects because it breaks up multi-unit characters (see the description of \eC +in the .\" HREF \fBpcrepattern\fP .\" documentation). The use of \eC is not supported in the alternative matching -function \fBpcre_dfa_exec()\fP, nor is it supported in UTF-8 mode by the JIT -optimization of \fBpcre_exec()\fP. If JIT optimization is requested for a UTF-8 -pattern that contains \eC, it will not succeed, and so the matching will be -carried out by the normal interpretive function. +function \fBpcre[16]_dfa_exec()\fP, nor is it supported in UTF mode by the JIT +optimization of \fBpcre[16]_exec()\fP. If JIT optimization is requested for a +UTF pattern that contains \eC, it will not succeed, and so the matching will +be carried out by the normal interpretive function. .P 6. The character escapes \eb, \eB, \ed, \eD, \es, \eS, \ew, and \eW correctly test characters of any code value, but, by default, the characters that PCRE -recognizes as digits, spaces, or word characters remain the same set as before, -all with values less than 256. This remains true even when PCRE is built to -include Unicode property support, because to do otherwise would slow down PCRE -in many common cases. Note in particular that this applies to \eb and \eB, -because they are defined in terms of \ew and \eW. If you really want to test -for a wider sense of, say, "digit", you can use explicit Unicode property tests -such as \ep{Nd}. Alternatively, if you set the PCRE_UCP option, the way that -the character escapes work is changed so that Unicode properties are used to -determine which characters match. There are more details in the section on +recognizes as digits, spaces, or word characters remain the same set as in +non-UTF mode, all with values less than 256. This remains true even when PCRE +is built to include Unicode property support, because to do otherwise would +slow down PCRE in many common cases. Note in particular that this applies to +\eb and \eB, because they are defined in terms of \ew and \eW. If you really +want to test for a wider sense of, say, "digit", you can use explicit Unicode +property tests such as \ep{Nd}. Alternatively, if you set the PCRE_UCP option, +the way that the character escapes work is changed so that Unicode properties +are used to determine which characters match. There are more details in the +section on .\" HTML .\" generic character types @@ -163,6 +217,6 @@ Cambridge CB2 3QH, England. .rs .sp .nf -Last updated: 19 October 2011 -Copyright (c) 1997-2011 University of Cambridge. +Last updated: 13 January 2012 +Copyright (c) 1997-2012 University of Cambridge. .fi